Bunsen monochromator

Emission spectroscopy utilizes the characteristic line emission from atoms as their electrons drop from the excited to the ground state. The earliest version of emission spectroscopy as applied to chemistry was the flame test, where samples of elements placed in a Bunsen burner will change the flame to different colors (sodium turns the flame yellow calcium turns it red, copper turns it green). The modem version of emission spectroscopy for the chemistry laboratory is ICP-AES. In this technique rocks are dissolved in acid or vaporized with a laser, and the sample liquid or gas is mixed with argon gas and turned into a plasma (ionized gas) by a radio frequency generator. The excited atoms in the plasma emit characteristic energies that are measured either sequentially with a monochromator and photomultiplier tube, or simultaneously with a polychrometer. The technique can analyze 60 elements in minutes. 

Monochromators (a) Czerny-Turner grating monochromator, (b) Bunsen prism monochromator. 

Figure 25-6 Types of monochromators (a) grating monochromator (b) prism monochromator. The monochromator design in (a) is a Czemy-Turaer design, while the prism monochromator in (b) is a Bunsen design. In both cases,...

FIGURE 7-18 Two types of monochromators, (a) Czerney-Tumer grating monochromator and (b) Bunsen prism rnonochromalor. (In bolh instances, a, > Ac.)... 

As shown in Figure 7-20b, the IMirow prism, which permits more compact monochromator designs, is a 30° prism with a mirrored back. Refraction in this type of prism takes place twice at the same interface so that the performance characteristics are similar to those of a 60° prism in a Bunsen mount. 

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